Are you able to recommend a dwarf ornamental tree possibly weeping varieties resistant to wilt. I have lost two Japanese maples. The space faces south, gets 65-75% sun (large maple provides some sunblock) and sits in front of a cedar hedge.
Thank-you for contacting Toronto Master Gardeners with your question about ornamental trees. Verticillium wilt is a fungal disease that affects many plant families. It does not generally respond to treatment. The best practice is to avoid the disease by selecting plants from resistant families/genus or resistant cultivars within plant families. Some of the trees you need to be careful about are: almonds and cherries (Prunus), maples (Acer – as you have experienced with your Japanese maples), redbud (Cercis), lilac (Syringa), Smokebush (Cotinus), Viburnum. Two families which are generally resistant are apple (Malus), including crabapples, and dogwood (Cornus). While there are lovely small trees in all of these families and resistant cultivars even in the susceptible groups, you would probably be wise to go with a selection from either Malus or Cornus. The verticillium fungus overwinters in the soil and can re-emerge into a favourable host.
It is important to keep in mind that even plants resistant to wilt may be susceptible to other significant problems. Crabapples, for instance, as members of the apple family (Malus), are resistant to wilt, but they are prone to other diseases such as apple sab, fire blight, and cedar apple rust. (If your cedar hedge is Eastern red cedar (Juniperus virginiana), do be cautious of this disease.) A couple of disease resistant and beautiful cultivars you may want to check out are Malus ‘Prairifire’ and M. ‘Sargentii’.
Dogwoods are another option for your garden. Again, you can find lists of cultivars that will bring good disease resistance as well as beautiful ornamental attributes to your garden. Cornus kousa species and cultivars seem to be more disease-resistant then the North American Cornus florida group.
Prior to going shopping, the best advice is to develop a list of shrubs and/or dwarf trees you like and then research them online to ascertain their disease resistance. If you are interested in crabapples or dogwoods, you might wish to review the following resources:
The following link is to a more general article on verticillium wilt with lists of susceptible and resistant plants:
Good luck making your choice!